Tweak null move pruning conditions

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index 2072c4bc241d7590d8dca47ba04e3e2c6985146b..744bb7886c5a2f06749faf41e23e68445f25e32c 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -737,6 +737,7 @@ namespace {
     // Step 9. Null move search with verification search (~40 Elo)
     if (   !PvNode
         && (ss-1)->currentMove != MOVE_NULL
+        && (ss-1)->statScore < 30000
         &&  eval >= beta
         &&  ss->staticEval >= beta - 36 * depth / ONE_PLY + 225
         && (ss->ply >= thisThread->nmp_ply || ss->ply % 2 != thisThread->nmp_odd))